iframe-loading-lazy-multiple-queued-navigations.html

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This WPT test may be referenced by the following Test IDs:
- /html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy-multiple-queued-navigations.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<head>

  <title>Multiple queued lazy load navigations do not crash the page</title>

  <link rel="author" title="Dom Farolino" href="mailto:dom@chromium.org">

  <link rel="help" href="https://html.spec.whatwg.org/multipage/urls-and-fetching.html#lazy-loading-attributes">

  <script src="/resources/testharness.js"></script>

  <script src="/resources/testharnessreport.js"></script>

</head>

<script>

  const t = async_test('Multiple queued lazy load navigations do not crash ' +

                       'the page');

  let has_below_viewport_loaded = false;

  window.addEventListener("load", t.step_func(() => {

    assert_false(has_below_viewport_loaded,

                "The below_viewport element should not have loaded before " +

                "window.load().");

    // Queue another lazy load navigation on the iframe. This should not result

    // in multiple internal intersection observers being created for the iframe

    // element, but instead should result in only one intersection observer

    // associated with the iframe element, and the resulting navigation should

    // be for the latest `src` attribute mutation.

    const target = document.querySelector('#below_viewport');

    target.src = 'resources/subframe.html?new-src';

    target.scrollIntoView();

  }));

  const below_viewport_iframe_onload = t.step_func_done(() => {

    const target = document.querySelector('#below_viewport');

    // We check both of these to ensure that the `src` attribute and actual

    // navigated resource do not get out-of-sync when navigating to lazy loaded

    // resources.

    assert_true(

      target.src.includes('new-src'),

      "The iframe's src should be updated to reflect the latest `src` " +

      "mutation");

    assert_true(

      target.contentDocument.location.href.includes('new-src'),

      'The iframe should be navigated to the resource provided by the latest ' +

      '`src` mutation');

});

</script>

<body>

  <div style="height:3000vh;"></div>

  <iframe id="below_viewport" src="resources/subframe.html?old-src"

          loading="lazy" width="200px" height="100px"

          onload="below_viewport_iframe_onload();"></iframe>

</body>